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Chemistry A Level > 1.3 Structure And Bonding > Flashcards

1.3 Structure And Bonding Flashcards

1
Q

What first must happen for an ionic bond to be formed?

A

An initial electron transfer to make full outer shells, with metal atoms losing electrons (forming positive cations) and non metals gaining electrons (forming negative anions)

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2
Q

What are the forces in ionic bonds?

A

The electrostatic attraction between oppositely charged ions

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3
Q

What is the structure in ionic bonding?

A

A giant Crystal lattice

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4
Q

Give the properties of an ionic compound

A
  • High melting and boiling point (many strong bonds which require a lot of heat energy to break)
  • Non conductors when solid (as charge is held in place
  • Conductive when molten or aqueous as ions are free to move and can carry charge
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5
Q

What does covalent bonding involve?

A

Sharing a pair of electrons to make a full outer shell, occurring between non-metal atoms.

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6
Q

Give properties of covalent bonds

A
  • Low melting and boiling point, as only intermolecular forces need to be broken
  • Non conductors when solid
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7
Q

What does metallic bonding involve?

A

Attraction between the lattice of positive metal ions and their delocalised outer shell electrons

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8
Q

Give properties of metallic bonding

A
  • High electro and thermal conductivity (as electrons can carry charge)
  • strong electrostatic attraction increases the m+b points
  • layers can be moved, causing it to be ductile and malleable
  • sea of electrons are responsible for the shininess, as they can absorb photons and re-emit them
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9
Q

What is electro negativity?

A

The ability of an atom to attract the electrons towards it in a covalent bond

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10
Q

What factors affect electro negativity ?

A
  • nuclear charge (more protons, stronger attraction)
  • atomic radius (closer to the nucleus, stronger attraction)
  • Shielding (less shells of electrons, more attraction)
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11
Q

What is the trend in electro negativity down a group?

A

Atomic radius increases, with more shielding, meaning there is less attraction between nucleus and bonding pair of electrons

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12
Q

What is the trend in electronegativity across a period?

A

Atomic radius decreases, more nuclear charge, causes stronger attraction between the nucleus and bonding pair of electrons.

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13
Q

What is the most electronegative element?

A

Fluorine

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14
Q

What does an electronegative difference of ~0.6 show?

A

A polar covalent bond

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15
Q

What does an electronegative difference of 0 show?

A

A completely covalent bond

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16
Q

What is the trend in melting points as the difference in electronegativity decreases?

A

A decrease in melting point as they move from hydrogen bonds, to dipole, to Van Dee Waal’s

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17
Q

What are the three intermolecular forces?

A
  • Wan der Waal’s
  • permanent dipole forces
  • Hydrogen bonding
18
Q

Describe Wan der Waal’s forces

A

They are the weakest intermolecular force, caused by the constant motion of electrons leading to uneven distribution of electrons, causing a “temporary dipole”, which induces a dipole on another molecule.

19
Q

Describe permanent dipole-dipole forces

A

Attraction between two polar molecules, negative end of one polar molecule attracts the positive end of another polar molecule. Greater differences in electronegativity leads to a stronger dipole force.

20
Q

Describe Hydrogen bonding

A

A special type of dipole bond that involves molecules in which Hydrogen is bonded to N, O or F. It is the strongest intermolecular force, and results in higher boiling points and viscosity

21
Q

What are the two types of electron pairs?

A

Bonding pairs (ie in a covalent bond) or non bonding pairs (lone)

22
Q

What is the trend in repulsion in types of electron pairs?

A

Bond-bond < bond-lone < lone-lone

23
Q

What is the shape of a molecule with 2 electron pairs with 2 of them being bonding pairs, and no lone pairs? + what is the bond angle + give an example.

A

Linear molecule
180°
(AX2) eg BeCl2, CO2

24
Q

What is the shape of a molecule with 3 electron pairs with 3 of them being bonding pairs, and no lone pairs? + what is the bond angle + give an example.

A

Trigonal planar
120°
(AX3) BF3

25
Q

What is the shape of a molecule with 3 electron pairs with 2 of them being bonding pairs, and 1 lone pair? + what is the bond angle

A

Bent V-shape

118°

26
Q

What is the shape of a molecule with 4 electron pairs with 4 of them being bonding pairs, and no lone pairs? + what is the bond angle + give an example.

A

Tetrahedral shape
109°
(AX4) eg CH4

27
Q

What is the shape of a molecule with 4 electron pairs with 3 of them being bonding pairs, and 1 lone pair? + what is the bond angle + give an example.

A

Pyramidal shape
107°
(AX3e)

28
Q

What is the shape of a molecule with 4 electron pairs with 2 of them being bonding pairs, and 2 lone pairs? + what is the bond angle + give an example.

A

Bent shape
104.5°
(AX2e2) H2O

29
Q

What is the shape of a molecule with 5 electron pairs with 5 of them being bonding pairs, and no lone pairs? + what is the bond angle + give an example.

A

Trigonal pyramidal
90° and 119°
PF5

30
Q

What is the shape of a molecule with 5 electron pairs with 3 of them being bonding pairs, and 2 lone pairs? + what is the bond angle

A

Trigonal planar or T-shape

120° or 89°

31
Q

What is the shape of a molecule with 6 electron pairs with 6 of them being bonding pairs, and no lone pairs? + what is the bond angle + give an example.

A

Octahedral
90°
SF6

32
Q

What is the shape of a molecule with 6 electron pairs with 4 of them being bonding pairs, and 2 lone pairs? + what is the bond angle?

A

Square planar

90°

33
Q

What is VSEPRT

A 
Valence
Shell 
Electron
Pair 
Repulsion 
Theory
34
Q

Describe VSEPRT.

A

1) determine the central atom
2) write down the group number
3) add one electron for each bond formed
4) allow for any ion charge
5) divide by 2 to fund number of electron pairs
6) work out number of bonding pairs
7) total pairs - bonding pairs

35
Q

Give an example of using VSEPRT.

A

Eg CH4
C=4
4 Bonds, 8 electrons, /2 = electron pairs. 4 bonds so 4 bond pairs, 4-4=0, so it is tetrahedral

36
Q

What is latent heat

A

When a substance is changing state the temperature remains the same, because the heat energy is being supplied to break the attractive forces between the particles

37
Q

What is the enthalpy change when one mole of a substance turns from a solid to a liquid?

A

The latent heat of fusion

38
Q

What is the enthalpy change when one mole of a substance turns from a liquid is turned into a gas?

A

Latent heat of vaporisation

39
Q

What is the bond angle in benzene?

A

120°

40
Q

What is the bond angle in cyclohexane?

A

109.5°

Chemistry A Level (35 decks)

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